Chapter 43 - Antioxidant Functions of Green and Black Tea

Abstract

Tea ( Camellia sinensis ) is the most popular beverage worldwide, after water. A number of population studies suggest that consumption of green and black tea beverages may bring possible health effects. One hypothesis explaining such effects is that the high levels of flavonoids in tea can protect cells and tissues from oxidative damage by scavenging oxygen-free radicals. Chemically, the flavonoids, particularly the catechins found in green and black tea are very effective radical scavengers. A substantial number of human intervention studies with green and black tea have demonstrated a significant increase in plasma antioxidant capacity in humans ~1 h after consumption of moderate amounts of tea (2 g solids in 300 ml water). In this regard, some in vitro studies using human blood showed increased lipid peroxidation, and attenuation of the microviscosity of erythrocytes after treatment with black tea extract or catechins. Similarly, phenylhydrazine treatment of goat erythrocytes to increase lipid peroxidation was inhibited by green tea extract. There are initial indications that enhanced blood antioxidant potential leads to a reduction in oxidative damage of macromolecules such as lipids and DNA. However, the assay systems used for measurements of oxidative damage through biomarkers needs to be developed further, and the quality of the studies currently available is insufficient to draw final conclusions, and further evidence from human intervention studies is required.